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在密之根州（美国）南半岛北部地区林龄大约９０年的北红橡（ｎｏｒｔｈｅｒｎｒｅｄｏａｋ，ＱｕｅｒｃｕｓｒｕｂｒａＬ．）林中，调查了北红橡幼苗外生菌根形态类型。实验地的立地质量为中等水平。通过砍伐不同数量的上层林木，形成０％（皆伐）、２５％（第一年５０％）、７５％、１００％（高度郁闭）４种林冠郁闭度。北红橡幼苗是由模仿自然更新人工播育种出，种源一致。在头２年，将幼苗上的外生菌根分类、描述和计数，同时收集菌根菌子实体进行鉴定和分析。根据形态特征，将外生菌根分为７个类型，其中４个类型占菌根总数的９４％。据现有资料（已发表的论文及图片等），把这些菌根类型的共生菌种或菌种组归纳。发现，在林冠高度郁闭并由此降低土壤水分的情况下，类型Ⅲ的菌根最多，表明这类菌根具有耐旱性；类型Ⅰ的菌根在皆伐区最多，表明其有耐较高土壤温度能力，因为皆伐后土壤温度比对照林分高出５℃以上。菌根类型随林冠郁闭度变化而变化的现象，反映了菌根关系的复杂性和多样性。本研究结果表明，探明菌根的形态类型比探明菌根菌的种类更有意义。
In the Northern Red Oak (northern red oak, Quercus rubra L.) forest, located in the northern part of the southern peninsula of Michigan in the State of Michigan (USA), the ectomycorrhizal morphological types were investigated. The site quality of the experiment is medium level. By cutting different numbers of upper trees, canopy density of 0% (clear cutting), 25% (first year 50%), 75%, 100% (highly canopy) canopy density was formed. North red rubber seedlings are artificial reproductive imitation of natural regeneration of species, the same provenance. In the first two years, the ectomycorrhiza on the seedlings were classified, described and counted, and the mycorrhizal fungi were collected for identification and analysis. According to the morphological characteristics, ectomycorrhizal fungi were divided into seven types, of which four types accounted for 94% of the total number of mycorrhiza. According to available information (published papers and pictures, etc.), we summarize these kinds of mycorrhizal symbionts or strains. It was found that the highest mycorrhizal type III was found under high canopy closure and hence soil moisture, suggesting that these mycorrhizas had drought tolerance; mycorrhizal type I was the most abundant in the clear cutting area, indicating that it was resistant High soil temperature capacity, because clear-cut soil temperature after the control of more than 5 ℃ above the control. The phenomenon that mycorrhizal types change with canopy density change reflects the complexity and diversity of mycorrhizal relationship. The results of this study show that the morphological types of the identified mycorrhizal fungi than the species of mycorrhizal fungi more meaningful.